To assess future climate change, it is important to have an understanding of future long-term emissions. Model-based scenarios are often used for this purpose. A new study published in ‘Nature Climate Change’ has brought together 6 different energy-economy-climate modeling teams to look at the sensitivity of future CO2 emissions to the major drivers. Economic growth and energy intensity are found to be the most important determinants of future CO2 emission.

The sensitivity of future emissions to major socio-economic and technical changes

CO2 emissions from energy combustion are the biggest determinant of man-made climate change; they have been growing over the past decades. In order to understand future climate change better, it is important to know how these emissions could develop. Scenarios based on energy-economy-climate models are designed to do this. These scenarios, however, are uncertain. In the new Nature Climate Change publication, researchers have collaborated to identify how future emissions are influenced by projections for population, income, energy intensity, fossil resources availability, and low carbon technologies and the associated uncertainty.

The study has confronted 3 possible future worlds: a sustainable, middle-of-the-road, and a challenging world. Using advanced statistical approaches, the study has disentangled the impacts of each of the above-mentioned drivers in isolation as well as in interaction with the others. One of the models included in the study is the PBL IMAGE model, used earlier to support the assessment of IPCC.

The study has built upon the Shared Socio-economic Pathways (SSPs). These scenarios represent assumptions with increasing challenges to mitigating and adapting to climate change. The scenarios present a wide range of possible developments for the economy, population, technology and the energy and land-use system. So-far, however, a systematic assessment of the sensitivity of these scenarios to the key drivers of change was still lacking. The Nature Climate Change publication aims to fill this gap.

Income and energy efficiency are key determinants of future emissions.

The study was led by researchers from FEEM (Milan) and the Politecnico di Milano. Researchers from PBL Netherlands Environmental Assessment Agency (Detlef van Vuuren and David Gernaat) were among the international experts contributing to this study.

The researchers highlight that the results clearly point to income and energy efficiency as key determinants of future emissions. It is also important to note that the different drivers interact: for example, a richer world will lead to lower emission increase if it is a sustainable one, and vice versa. The results of the study can be used to identify effective policies – and for instance point at the importance of energy efficiency.

The uncertainty ranges spanned by the scenario story-lines and the different modelling choices in implementing them have the potential to influence several years of climate policy research to come. The study helps prioritizing this research, suggesting that modelling and policy communities could benefit from shifting part of their attention from the traditional energy-supply domain also to elements like energy efficiency and economic wellbeing.